Fiber Bragg grating (FBG) sensors used in coal mines

Abstract

The fiber Bragg grating (FBG) strain sensors were used for on-line monitoring of the stress variation of the lined wall in the gateway retained along the goaf of No. 3203 coal mining face in Dongtan Mine. The results showed that the FBG strain sensor with the wide measuring range could measure the stress variation accurately during the support process of the gateway retained along the goaf and could provide the basis to further optimize the support structure and to determine the support plan of the gateway retained along the goaf. The FBG micro-seismic sensors were used in Xinglong Mine to detect the micro-seismic signal. The signals were well received and analyzed to determine the location and energy level of the source of the micro-seismic event warning. The FBG sensors and detecting system show a significant potential for micro-seismic detection and geological disasters detection.

FBG based high sensitive pressure sensor and its low-cost interrogation system with enhanced resolution

“… is the effective strain-optic constant, 11 P and 12 P are the components of strain-optic constant, and υ is Poisson's ratio. The second term in (2), represents the temperature effect, where Λ α and n ξ are the thermal expansion coefficient and thermo-optic coefficient of the fiber.…”

“…In contrast, fiber Bragg grating (FBG)-based fiber optic sensors have significant advantages over conventional sensors such as the small size, lightweight, large dynamic range, immunity to EMI, high sensitivity and accuracy, ease to embed in civil structures, chemical inertness, and remote sensing capability. Moreover, the multiplexing property of FBG sensors makes them potential candidates for spatially distributed measurements [6][7][8][9][10][11]. However, the pressure sensitivity of a bare FBG (-0.022 pm/psi) is very low, which is to be greatly enhanced [12].…”

Spectra power and bandwidth of fiber Bragg grating under influence of gradient strain

“…As an important wavelength sensitive device, a fiber Bragg grating (FBG) has been widely studied and applied [1][2][3][4][5]. Most of the researches focus on the wavelength sensing technology and theory, but when the inhomogeneous field applying on the FBG, such as the gradient stain and gradient temperature, acts on the grating range of the FBG, which can lead to the FBG chirping, and the reflective spectrum shows new features, such as reflective power and reflective bandwidth [6][7][8][9][10].…”

Design of fiber magnetic field sensor based on fiber Bragg grating Fabry-Perot cavity ring-down spectroscopy

“…The fiber magnetic sensor has attracted considerable interest for its advantages of the high sensitivity, simple structure, light weight, easy to make, low cost, long working distance [1][2][3][4][5][6], etc. Till now, many possibilities have been proposed to generate the fiber magnetic sensor, such as the Mach-Zehnder interferometer in the open-loop mode [7], metallic glass with the detection technique utilizing a square-wave magnetic field modulation [8], and fiber optic Michelson interferometer [9].…”